title: The essential cytosolic iron-sulfur protein Nbp35 acts without Cfd1 partner in the green lineage.
abstract: In photosynthetic eukaryotes assembly components of iron-sulfur (Fe-S) cofactors have been studied in plastids and mitochondria, but how cytosolic and nuclear Fe-S cluster proteins are assembled is not known. We have characterized a plant P loop NTPase with sequence similarity to Nbp35 of yeast and mammals, a protein of the cytosolic Cfd1-Nbp35 complex mediating Fe-S cluster assembly. Genome analysis revealed that NBP35 is conserved in the green lineage but that CFD1 is absent. Moreover, plant and algal NBP35 proteins lack the characteristic CXXC motif in the C terminus, thought to be required for Fe-S cluster binding. Nevertheless, chemical reconstitution and spectroscopy showed that Arabidopsis (At) NBP35 bound a [4Fe-4S] cluster in the C terminus as well as a stable [4Fe-4S] cluster in the N terminus. Holo-AtNBP35 was able to transfer an Fe-S cluster to an apoprotein in vitro. When expressed in yeast, AtNBP35 bound 55Fe dependent on the cysteine desulfurase Nfs1 and was able to partially rescue the growth of a cfd1 mutant but not of an nbp35 mutant. The AtNBP35 gene is constitutively expressed in planta, and its disruption was associated with an arrest of embryo development. These results show that despite considerable divergence from the yeast Cfd1-Nbp35 Fe-S scaffold complex, AtNBP35 has retained similar Fe-S cluster binding and transfer properties and performs an essential function.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom.
authors.forename: Katrine
authors.initials: K
authors.lastname: Bych
authors.forename: Daili J A
authors.initials: DJ
authors.lastname: Netz
authors.forename: Gianpiero
authors.initials: G
authors.lastname: Vigani
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.forename: Roland
authors.initials: R
authors.lastname: Lill
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Pierik
authors.forename: Janneke
authors.initials: J
authors.lastname: Balk
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018745:Genome, Plant / Q000502:physiology; D024101:Mitochondrial Proteins; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D013466:Sulfurtransferases
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D024101:Mitochondrial Proteins; D046912:Multiprotein Complexes; C534471:Nbp35 protein, Arabidopsis; D029701:Saccharomyces cerevisiae Proteins; D013466:Sulfurtransferases; C115912:NFS1 protein, S cerevisiae; D013437:Carbon-Sulfur Lyases; C080546:cysteine desulfurase